I have built and tested Perl 5.8.6 and 5.9.1 under BeOS R5 x86 net server.
I can't say anything with regard to PPC.
Since Perl 5.8.0 had been released for BeOS BONE,
I suspect,
there is a good chance,
that it still compiles on a BONE system.
The only change I've made,
that affects BONE systems is the recognition of whether it is a BONE system or not in hints/beos.sh.
Now network socket support should remain enabled on BONE systems.
This might as well break the build,
though.

As more recent versions of autoconf require flock() support,
I wrote a flock() emulation (flock_server) and released it on BeBits:

Network socket support is disabled for BeOS R5 net server. I didn't dare yet to try enabling it and see what problems occur.

The LFS (large file support) tests (t/op/lfs and xt/Fcntl/t/syslfs) are disabled as seeking beyond 2 GB is broken according to jhi@iki.fi who was the last one checking the BeOS port and updating this file before me. Haven't checked this myself.

The t/io/fflush test fails at #6. As far as I can tell, this is caused by a bug in the BeOS pipes implementation that occurs when starting other child processes. In the particular test case a system("perl -e 0") flushes the stdout pipe of another child process.

The ext/POSIX/t/waitpid test fails at #1. After all child processes are gone BeOS' waitpid(-1,...) returns 0 instead of -1 (as it should). No idea how to fix this.